How the laws of physics constrain the size of alien raindrops
The size of raindrops is similar no matter what they’re made of or what planet they fall on
Whether they’re made of methane on Saturn’s moon Titan or iron on the exoplanet WASP 76b, alien raindrops behave similarly across the Milky Way. They are always close to the same size, regardless of the liquid they’re made of or the atmosphere they fall in, according to the first generalized physical model of alien rain.
“You can get raindrops out of lots of things,” says planetary scientist Kaitlyn Loftus of Harvard University, who published new equations for what happens to a falling raindrop after it has left a cloud in the April Journal of Geophysical Research: Planets. Previous studies have looked at rain in specific cases, like the water cycle on Earth or methane rain on Saturn’s moon Titan (SN: 3/12/15). But this is the first study to consider rain made from any liquid.
“They are proposing something that can be applied to any planet,” says astronomer Tristan Guillot of the Observatory of the Côte d’Azur in Nice, France. “That’s really cool, because this is something that’s needed, really, to understand what’s going on” in the atmospheres of other worlds.
Comprehending how clouds and precipitation form are important for grasping another world’s climate. Cloud cover can either heat or cool a planet’s surface, and raindrops help transport chemical elements and energy around the atmosphere.